From 1995 to 1999 we evaluated questionnaires sent by pulmonologists and departments of pulmonology in order to register interstitial lung diseases. On the whole 1142 patients (579 males, 563 females, mean age 51.1 +/- 15.3 years, sarcoidosis, n = 511, extrinsic allergic alveolitis, n = 145, idiopathic pulmonary fibrosis, n = 308, bronchiolitis obliterans organizing pneumonia (BOOP), n = 93, others, n = 85) were recorded in the registry. With reference to the mean age sarcoidosis occurred most frequently in the fourth decade and idiopathic pulmonary fibrosis in the sixth decade. In all these diseases bronchoscopy with bronchoalveolar lavage and transbronchial biopsy was predominantly used for further diagnosis. It was striking that high-resolution computed tomography of the thorax was still rarely used when diagnosing these diseases. Apart from the group with BOOP the number of non-smokers in men and women was decisively higher than the average of the population of Germany.